EEPM523 POWER SYSTEM DYNAMICS
Aznan Ezraie AriffinUNITEN
Semester 1, May Sept 2014
Presentations: 3 July 2014
Voltage Control in Power Systems
Reactive power must be balanced so as that the voltages are within acceptable limits
Improper reactive power balance will result in deviations of the voltages
Normally the power system is operated such that the voltage drops along the lines are smaller and the node
2
voltage drops along the lines are smaller and the node voltages of the system are almost equal
Voltage magnitudes can be controlled to desired values by control of the reactive power
There are several sources of reactive power but it cannot be transported over long distances in the system
Voltage Control in Power Systems (cont) Important generators of reactive power:
Overexcited synchronous machines Capacitor banks Capacitance of overhead lines and cables FACTs devices
Important consumers of reactive power:
3
Important consumers of reactive power: Inductive static loads Underexcited synchronous machines Induction motors Inductance of overhead lines and cables Transformer inductances FACTs devices
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
4
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
The functions of an excitation system are:
To provide direct current to the synchronous generator field winding
To perform control and protective functions essential to the satisfactory
5
functions essential to the satisfactory operation of the power system
The performance requirements of the excitation system are determined by:
Generator considerations Supply and adjust field current as the generator output varies
within its continuous capability Respond to transient disturbances with field forcing consistent
with generator short term capabilities: Rotor insulation failure due to high field voltage
6
Rotor insulation failure due to high field voltage Rotor heating due to high field current Stator heating due to high VAR loading Heating due to excess flux (volts/Hz)
Power System considerations: Contribution to effective control system voltage and improvement
of system stability
Performance requirements of an excitation system
- meet specified response criteria- provide limiting and protection to prevent damage to
To fulfill the above roles satisfactorily, the excitation system must satisfy the following requirements:
7
- provide limiting and protection to prevent damage to itself, the generator, and other equipment
- meet specified requirements for operating flexibility- meet the desired reliability and availability
Functional block diagram of a synchronous generator excitation control system
8
Evolution of excitation systems
- Early exciters were controlled manually
- In the 1920s, continuous and fast acting regulators contributed to improvements in steady-state and transient stability
- In the 1960s,the role of excitation systems expanded by use
9
- In the 1960s,the role of excitation systems expanded by use of power system stabilizer
- Modern exciters are capable of practically instantaneous response with high ceiling voltages with a wide array of control and protective circuits
- Digital excitation system are widely utilized.
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
10
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Types of Excitation Systems
Classified into 3 broad categories based on the excitation power source:
DC excitation systemsAC excitation systemsStatic excitation systems
11
Static excitation systems
DC Excitation Systems
Utilise DC generators as source of power; driven by a motor or the shaft of main generator
Represents early systems (1920s to 1960s); lost favour in the mid-1960s because of large size; superseded by AC exciters
Voltage regulators range from the early non-continuous rheostatic type to the later systems using magnetic and rotating amplifiers
12
Self-excited DC exciter supplies current to the main generator field through slip rings
Exciter field controlled by an amplidyne which provides incremental changes to the field in a buck-boost scheme
The exciter output provides rest of its own field by self-excitation
13
An example of direct current excitation system
Self-excited (main field connected across the terminals of the exciter armature). Two control fields, one assists the main field, the other reduces the main field, referred as a
boost-buck scheme. The power of control fields is supplied by a pilot exciter (permanent magnet generator),
through the AVR.
DC excitation system with an amplidyne voltage regulator
14
AC Excitation Systems
Use AC machines (alternators) as source of power Usually, the exciter is on the same shaft as the turbine-generator
The AC output of the exciter is rectified by either controlled or non-controlled rectifiers
15
Rectifiers may be stationary or rotating Early systems used a combination of magnetic and rotating amplifiers as regulators; most new systems use electronic amplifier regulators
AC Excitation Systems: stationary type
DC output to the main generator field supplied through slip rings
When non-controlled rectifiers are used, the regulator controls the field of the AC exciter (GE-ALTERREX)
When controlled rectifiers are used, the regulator directly controls the DC output voltage of the exciter
16
directly controls the DC output voltage of the exciter (GE-ALTHYREX)
Field controlled alternator rectifier excitation system (GE-ALTERREX)
17
Alternator supplied controller-rectifier excitation system (GE-ALTHYREX)
18
AC Excitation Systems: rotating type
The need for slip rings and brushes is eliminated; such systems are called brushless excitation systems
They were developed to avoid problems with the use of brushes perceived to exist when
19
use of brushes perceived to exist when supplying the high field currents of large generators
They do not allow direct measurement of generator field current or voltage
Brushless excitation system
20
Static Excitation Systems
All components are static or stationary Supply DC directly to the field of the main generator through slip rings
The power supply to the rectifiers is from the main generator or the station auxiliary bus
21
main generator or the station auxiliary bus
Static Excitation Systems: potential-source controlled
Excitation power is supplied through a transformer from the main generator terminals
Regulated by a controlled rectifier Commonly known as bus-fed or transformer-fed static excitation system
22
Very small inherent time constant Maximum exciter output voltage is dependent on input AC voltage; during system faults the available ceiling voltage is reduced
Potential-source controlled rectifier excitation system
23
Static Excitation Systems: compound-source
Power to the exciter is formed by utilising current as well as voltage of the main generator
Achieved through a power potential transformer (PPT) and a saturable current transformer (SCT)
The regulator controls the exciter output through controlled saturation of excitation transformer
24
controlled saturation of excitation transformer During a system fault, with depressed generator voltage, the current input enables the exciter to provide high field forcing capability
Compound-source rectifier excitation system (GE SCT-PPT)
25
Static Excitation Systems: compound-controlled
Utilizes controlled rectifiers in the exciter output circuits and the compounding of voltage and current within the generator stator
Result in a high initial response static system with full fault-on forcing capability (GE
26
with full fault-on forcing capability (GE GENERREX)
Compound-controlled rectifier excitation system
27
Control and Protective Functions A modern excitation control system is much more than a simple
voltage regulator It includes a number of control, limiting and protective functions
which assist in fulfilling the performance requirements identified earlier
The following figure illustrates the nature of these functions and the manner in which they interface with each other
28
the manner in which they interface with each other Any given system may include only some or all of these functions
depending on the specific application and the type of exciter Control functions regulate specific quantities at the desired level Limiting functions prevent certain quantities from exceeding set limits If any of the limiters fail, then protective functions remove appropriate
components or the unit from service
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
29
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Elements of an Excitation System
1. Exciter: provides DC power to the generator field winding2. Regulator: processes and amplifies input control signals to a
level and form appropriate for control of the exciter3. Terminal voltage transducer and load compensator: senses
generator terminal voltage, rectifies and filters it to a DC quantity and compares with a reference;load compensator may be provided if desired to hold voltage at remote point
30
be provided if desired to hold voltage at remote point4. Power system stabiliser: provides additional input signal to
the regulator to damp power system oscillations5. Limiters and protective circuits: ensure that the capability
limits of exciter and generator are not exceeded
Voltage Sensing and Load Compensation
Voltage Sensing
Exciter GeneratorField Shorting
DC Regulator
AC Regulator
Exc. Sys. Stab. circuits
Adjuster
Adjuster
Excitation system control and protective circuits
31
Note: Field shorting circuits are applicable to ac and static exciters only Some systems have open loop dc regulator Max. exc. limiter may also be used with dc regulator
Power System Stabilizer
Max. Exc.Limiter
Under Exc. Limiter
V/Hz Limiter Protection
Var and/or PF Controller
Components of an Excitation System:AC Regulator: Basic function is to maintain generator stator voltage In addition, other auxiliaries act through the AC regulator
DC Regulator: Holds constant generator field voltage (manual control)
32
Holds constant generator field voltage (manual control) Used for testing and startup, and when AC regulator is faulty
Excitation system system stabilizing circuits: Excitation systems with significant time delays have poor inherent
dynamic performance Unless very low steady-state regulator gain is used, the control
action is unstable when the generator is on open-circuit
Components of an Excitation System (cont): Series or feedback compensation is used to improve the dynamic
response Most commonly used form of compensation is a derivative
feedback Static excitation systems have negligible inherent time delays and
do not require stabilization
33
lh}y+
-
EfdVe
B
C
sTsT
+
+
11
Transient Gain Reduction
Stabilization of Excitation Control System
34
The derivative feedback scheme is often used for rotating exciters, while the transient gain reduction scheme is for ac and static exciters Its not common for both schemes to be employed at the same time.
Derivative Feedback
F
F
sTsK+1
Components of an Excitation System (cont):Power System Stabilizer: Uses auxiliary stabilizing signals (such as shaft speed, frequency,
power) to modulate the generator field voltage so as to damp system oscillations
Load compensator: Used to regulate a voltage at a point either within or external to
the generator
35
the generator Achieved by building additional circuitry into the AVR loop With Rc and Xc positive, the compensator regulates a voltage at
a point within the generator used to ensure proper sharing VARs between generators bussed
together at their terminals commonly used with hydro units and cross-compound thermal units
Components of an Excitation System (cont): With Rc and Xc negative, the compensator regulates a voltage at
a point beyond the generator commonly used to compensate for voltage drop across step-up
transformer when generators are connected through individual transformers
36
Components of an Excitation System (cont):Underexcitation Limiter (UEL): Intended to prevent reduction of generator excitation to a level where steady-state stability limit or stator core end-region heating limit is exceeded
Control signal derived from a combination of either voltage or current or active and reactive power of the
37
voltage or current or active and reactive power of the generator
A wide variety of forms used for implementation Should be coordinated with the loss-of-excitation protection
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
38
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Coordination between UEL, LOE relay and stability limit
39
Components of an Excitation System (cont):Overexcitation Limiter (OEL): Purpose is to protect the generator from overheating due to
prolonged field over-current The figure next shows thermal overload capability of the field
winding OEL detects the high field current condition and, after a time
delay, acts through the AC regulator to ramp down the excitation
40
delay, acts through the AC regulator to ramp down the excitation to about 110% of rated field current; if unsuccessful, trips the AC regulator, transfers to DC regulator, and repositions the set point corresponding to rated value
Two types of time delays used fixed time and inverse time With inverse time, the delay matches the thermal capability (as
shown in the figure next)
Coordination of over-excitation limiting with field thermal capability
41
The measure of volts per hertz is an indication of the flux conditions in the generator stator core, which can be seen from the following equation:
Volts per Hertz Limiter and Protection
pi = tdr NkfE 2
42
pi = tdr NkfE 2Where
E = armature phase voltage (volts,rms),kd = distribution factor , fr = rotor speed (Hz) = flux in the machine core (megalines),Nt = effective number of series turn per armature phase per
circuit, linking the flux
Components of an Excitation System (cont):Volts per Hertz Limiter and Protection: Used to protect generator and step-up transformer from damage
due to excessive magnetic flux resulting from low frequency and/or overvoltage
Excessive magnetic flux, if sustained, can cause overheating and damage the unit transformer and the generator core
Typical V/Hz limitations:
43
Typical V/Hz limitations:V/Hz (p.u.) 1.25 1.2 1.15 1.1 1.05Damage Time in Minutes
GEN 0.2 1.0 6.0 20.0 inf
XFMR 1.0 5.0 20.0 inf
Components of an Excitation System (cont):
V/Hz limiter (or regulator) controls the field voltage so as to limit the generator voltage when V/Hz exceeds a preset value
V/Hz protection trips the generator when V/Hz exceeds the preset value for a specified time
44
exceeds the preset value for a specified time
Note: The unit step-up transformer low voltage rating is frequently 5% below the generator voltage rating
Modelling of Excitation Systems
Detail of the model required depends on the purpose of study: The control and protective features that impact on
transient and small-signal stability studies are the voltage regulator, PSS and excitation control stabilization
45
stabilization The limiter and protective circuits normally need to be
considered only for long-term and voltage stability studies.
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
46
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Dynamic Performance Measures
47
Representation of the overall excitation system in the classical form describing feedback control system
Performance of excitation control system depends on the characteristics of Excitation system Generator Power system
Large Signal Performance Measures
Provide a means of assessing the excitation system performance for severe transients
Performance measures are defined under specified conditions Ceiling voltage max direct voltage indicative of field forcing
capability Ceiling current max direct current
48
Voltage time response output voltage as function of time Voltage response time time in secs to attain 95% between
ceiling voltage and rated load field voltage High initial response response time of 0.1 secs or less Nominal reponse -
( )( )oeaocd
Large Signal Performance Measures
49
Excitation system nominal response
AB
C
D
Actual response
Nominal Response Ratio = CD /AO / 0.5
Note: The basis for considering a nominal time span of 0.5 seconds in
Large-signal Performance Measures
50
A D
EO Time in seconds
Area ABD = Area ACDOE = 0.5 secondsAO = Rated field voltage
E
x
c
i
t
e
r
o
u
t
p
u
t
v
o
l
t
a
g
e
nominal time span of 0.5 seconds in the definition is that, following a severe disturbance, the generator rotor angle swing normally peaks between 0.4 s and 0.75 s. The excitation system must act within this time period to be effective in enhancing transient stability. Accordingly 0.5 s was chosen for the definition.
Generally Accepted Values of SmallGenerally Accepted Values of Small--signal signal Indexes Characterizing Good Feedback Control Indexes Characterizing Good Feedback Control
System PerformanceSystem Performance
Gain Margin Gm : 6 dB (open-loop)Phase Margin m : 40 (open-loop)Overshoot: 0 ~ 15% (time step)Peak Value MP : 1.1 ~ 1.6 dB (closed loop)Damping Ratio: 0.6 (S-plane)
51
Small Signal Performance Measures
52Typical time response to step input
Small Signal Performance Measures
53
Typical open-loop frequency response with generator open circuited
Small Signal Performance Measures
54
Typical closed-loop frequency response with generator open circuited
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
55
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Modelling of Excitation System Components
The basic elements which form different types of excitation systems are:
DC exciters (self or separately excited) AC exciters Rectifiers (controlled or non-controlled) Amplifiers (magnetic, rotating or electronic)
56
Amplifiers (magnetic, rotating or electronic) Excitation system stabilizing feedback circuits Signal sensing and processing circuits
Block diagram of a DC exciter (page 351 PB)
57
For separately excited DC exciter, the value of KE is Ref/Rg For self-excited DC exciter, the value of KE is Ref/Rg - 1
Block diagram of AC exciter
58
Rectifier regulation model
59
Amplifiers
60
Amplidyne model (rotating amplifier)
61
Integrator with windup limits
62
Integrator with non-windup limits
63
Single time constant block with windup limits
64
Single time constant block with non-windup limits
65
Lead-lag function with non-windup units
66
Gating functions
u
v
67
Structure of a detailed excitation system model
68
IEEE Standard Exciter Models
- IEEE has standardized 12 model structures for representing the wide variety of excitation systems currently in use (see IEEE standard 421.5-1992)
- These models are intended for use in transient and small-signal stability studies.
Modeling of Limiters
69
Modeling of Limiters
- Standard models do not include limiting circuits; these do not come into play under normal conditions.
- These are, however, important for long-term and voltage stability studies
- Implementation of these circuits varies widely. Models have to be established on a case by case basis.
Type DC1A exciter model
70
Type AC1A exciter model
71
Type AC4A excitation system model
72
Type ST1A exciter model
73
Field current or over-excitation limiter
74
Field current limiter model
75
Digital Excitation Systems
There is a growing trend toward using the digital technology to perform control and protection functions of modern excitation systems
They are not just digital version of their analog
76
They are not just digital version of their analog counterparts, but contain sophisticated control functions not readily available in analog excitation systems
The use of digital systems are economically feasible Examples: GE EX2000, ABB Unitrol-F, Basler Decs
ExciterController
Scaling Circuitry
Set Point nnnn+-
Block Diagram of an Analog Excitation System
77
Block Diagram of a Digital Excitation System
ExciterController
Scaling Circuitry
Set Point nnnn+-
D/A
Microprocessor based digital systemA/D
Features of Digital Excitation Systems
Extremely sophisticated control strategy and algorithms can be readily implemented. They can be nonlinear, fuzzy logic, adaptive or any type of control.
The control and protection functions can be incorporated in the microprocessor codes, eliminating the need of using separate hardware
78
microprocessor codes, eliminating the need of using separate hardware devices:
- Power system stabilizer (PSS)- Var or power factor control (Var/PF)- Under and over excitation limiters (UEL/OEL)- Stator current limiter (SCL)- Volts per Hertz limiter (V/Hz)
Features of Digital Excitation Systems
Communication capability - Digital systems typically have some form of communications available to users, from the simplest local key pad and display, to more complex scheme such as local serial link, remote serial link, modem, local area network etc. The communication capability may be used to change controller parameter settings or exchange
79
used to change controller parameter settings or exchange data with other controllers in the system such as the speed governor or a supervisory controller.
Data recording The ability to record various parameters associated with the excitation system. It may output data to an external data recorder via D/A converters, or directly do the recording internally.
Features of Digital Excitation Systems
Metering Digital systems can provide the display of various generator system parameters that are not normally available on analog systems without including some additional transducers. It may be linked to a main computer to provide metering quantities.
80
computer to provide metering quantities.
Self test and system test many contain on-board test features.
Cost per function is typically lower for the digital system.
Off-line setup means reduced commissioning time.
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
81
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
AVR Step Response Test
82
IEEE Type ST1 Exciter Model Validated for the Static Excitation System
TR VIMAX VIMIN TC TB KA TA VRMAX VRMIN KC KF TF
0.02 0.1 -0.1 0.0 0.0 120 0.02 6.4 0.0 0.0 0.01 2.5
step applied here
step applied here
AVR Step Response Test
83
IEEET1 DC Exciter Model Validated for the Excitation System
Test Procedure:
Operate unit at full speed no load (off-line) Set exciter in AVR control Apply a step change (5% typical ) to the AVR set point
AVR Step Response Test
84
Apply a step change (5% typical ) to the AVR set point Repeat with a 10% step change, trying to hit the field
voltage ceiling and floor limits
0.95
0.96
0.97
0.98
0.99
1.00
S
t
a
t
o
r
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
3.0
4.0
5.0
6.0
7.0
F
i
e
l
d
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
Measured-Vt Simulated-Vt
Measured-Vf Simulated-Vf
AVR Step Response Test
85
AVR Step Test Results for a Potential-Source Static Excitation System
0.91
0.92
0.93
0.94
0.95
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Time in seconds
S
t
a
t
o
r
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
0.0
1.0
2.0
3.0
F
i
e
l
d
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
1.00
1.01
1.02
1.03
1.04
1.05S
t
a
t
o
r
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
1.0
1.5
2.0
2.5
F
i
e
l
d
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
AVR Step Response Test
86
AVR Step Test Results for a 80MVA Hydro Generator with a dc Exciter (Sample)
0.96
0.97
0.98
0.99
1.00
0 2 4 6 8 10 12 14 16 18 20
Time in seconds
S
t
a
t
o
r
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
0.0
0.5
1.0
F
i
e
l
d
v
o
l
t
a
g
e
i
n
p
e
r
u
n
i
t
Measured Vt Simulated VtMeasured Vf Simulated-Vf
Excitation Systems Need for Accurate Model
Since excitation systems play such an important rule in the characteristics of oscillations, their modelling is also critical
Appropriate excitation system models must be
87
Appropriate excitation system models must be developed
Typical model and data should not be usedThe least is to use the manufacturer recommended modelsIf possible, the models should be field tested and validated
Generator terminal voltage (pu)
1.040
1.060
1.080Generator terminal voltage (pu)
1.040
1.060
1.080
Sustained oscillations
IEEE AC5A type exciter
Rate feedback gain K (at
Exciter Step Response Examples (Contd)
88
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
Rate feedback gain KF (at 0.005) is too small
Setting KF to 0.05 makes response very reasonable
Generator terminal voltage (pu)
1.040
1.060
1.080Generator terminal voltage (pu)
1.040
1.060
1.080
Large swings
IEEE AC1A type exciter
Rate feedback time constant TF(at 0.017) is too small
Exciter Step Response Examples (Contd)
89
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020 Setting TF = 1.0 makes response very reasonable
Generator terminal voltage (pu)
1.040
1.060
1.080Generator terminal voltage (pu)
1.040
1.060
1.080
Very slow response
IEEE AC1A type exciter
Rate feedback time constant TFand gain KF are both at 2.9; apparently set incorrectly
Exciter Step Response Examples (Contd)
90
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
Fapparently set incorrectly
Setting TF = 1.0 and KF = 0.05 makes response more reasonable
Generator terminal voltage (pu)
1.060
1.080
1.100Generator terminal voltage (pu)
1.060
1.080
1.100
Large swings
The AVR has a PI controller
The proportional and integral gains (at 0.0357 and 3.57 respectively) are not appropriately
Exciter Step Response Examples (Contd)
91
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
1.040
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.000
1.020
1.040respectively) are not appropriately coordinated
Setting both of proportional and integral gains to 3.57 makes response more reasonable
Generator terminal voltage (pu)
1.100
1.130
1.160
Large overshoot
IEEE AC5A type exciter
The AVR gain KA is set at 2894 with a slow exciter time constant T (at 1.2 seconds). This
Exciter Step Response Examples (Contd)
92
Time (sec)0.000 2.000 4.000 6.000 8.000 10.000
0.980
1.010
1.040
1.070TE (at 1.2 seconds). This apparently is poorly coordinated
A transient gain reduction would possibly make the response better
13.95
14.00
14.05
14.10
T
e
r
m
i
n
a
l
v
o
l
t
a
g
e
i
n
k
V
Field testing is an effective way to validate exciter model as shown in the example with exciter step test
Exciter Step Response Examples (Contd)
93
13.60
13.65
13.70
13.75
13.80
13.85
13.90
13.95
0 1 2 3 4 5 6 7 8 9 10
Time in seconds
T
e
r
m
i
n
a
l
v
o
l
t
a
g
e
i
n
k
V
Measured responseSimulated (old model)Simulated (new model)
Exciter Step Response Examples Field test
94
12
14
16
18
20
R
e
a
c
t
i
v
e
P
o
w
e
r
,
Q
(
M
V
A
R
)
15.4
15.4
15.5
15.5
15.6
T
e
r
m
i
n
a
l
V
o
l
t
a
g
e
,
V
t
(
k
V
)
Exciter Step Response Examples Vt and Q response due to step input
95
0
2
4
6
8
10
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5Time (s)
R
e
a
c
t
i
v
e
P
o
w
e
r
,
Q
(
M
V
A
R
)
15.1
15.2
15.2
15.3
15.3
15.4
T
e
r
m
i
n
a
l
V
o
l
t
a
g
e
,
V
t
(
k
V
)
Q (MVAR) Vt
Topics on Excitation System
Excitation requirements Types of excitation systems Elements of an excitation system Control and corrective functions
96
Control and corrective functions Dynamic performances Modeling of excitation systems Step Responses Tests Review of Classical Control Techniques
Classical Control Technique
97
Open Circuit Response
98
Open Circuit Response
99
Open Circuit Response
100
Open Circuit Response
101
Open Circuit Response
102
Open Circuit Response
103
Open Circuit Response
104
Open Circuit Response
105
Open Circuit Response
106
Open Circuit Response
107
Open Circuit Response
108